1. Field of the Invention
The invention relates to an atomizer for a fluid whose droplets are precipitated onto a surface. The atomizer can atomize aqueous and non-aqueous fluids, emulsions and suspensions, solutions, dyes and oils. The atomizer can be miniaturized, and it can also contain micro-structured elements.
The atomizer according to the present invention does not require a propellant gas, can be actuated manually, and can be adapted to the properties of various fluids that are to be atomized, as well as to the planned application of the atomized fluid.
2. Description of the Related Art
Atomizers are known where the fluid under pressure contains a propellant (e.g., a liquefied propellant gas) with which the fluid is atomized upon exiting through a nozzle, such as by the influence of the evaporating propellant. Known propellants include gases that are physiologically hazardous, pollute the environment, or are flammable. The container for the fluid must withstand the gas pressure, possibly even at elevated temperatures, and be tight against the gas pressure. If during storage of the container, which is generally filled partially with the fluid, or during usage of the atomizer, the valve on the container is not sufficient gas-tight and the gas pressure drops due to the partially leaking gas, the usefulness of the container or the atomizer can be limited.
Atomizers are known in which the fluid is pushed through a nozzle by a pump, which is manually actuated by the operator, and is thus atomized. The pressure applied to the fluid that is to be atomized, and thus the distribution of the droplet size, is dependent upon the force with which the operator actuates the pump. Thus the pressure at which the fluid is atomized is dependent upon the behavior of the user. Actuation of such an atomizer can be difficult for a person lacking practice when the atomized fluid is supposed to be deposited at a specified location (for example on the skin of the user).
Another known atomizer includes an air pump and a container for the fluid that is to be atomized. The air pump includes a piston, which is moved manually back and forth inside a cylinder. Air flows out from a hole in the bottom of the cylinder. The fluid container is attached to the cylinder, which is equipped with a thin immersion tube, extending into the fluid in the fluid container. The other end of the immersion tube is located directly next to the hole in the bottom of the cylinder. The axis of the immersion tube is vertical in relation to the direction in which the air current exits the cylinder. With sufficient speed of the air flowing out of the container, the fluid experiences a suction effect and is carried along in the air current and atomized. The amount of fluid taken in during one stroke of the piston, and the distribution of the droplet sizes, depends on the speed with which the air exits the hole in the bottom of the cylinder. Both features are difficult to reproduce.
In the known atomizer with a manually actuated pump, the delivery amount and the average droplet size are dependent upon the behavior of the user. The pressure that can be attained is relatively low and is typically less than 0.8 MPa (8 bar). With whirl chamber nozzles, whose outlet orifices have a diameter of more than 300 micrometers, a discharge quantity that is suitable for the application purpose can be achieved with a relatively large mean or average particle size.
A miniaturized high-pressure atomizer is known from WO 97/12687, with which small quantities, e.g. 15 microliters, of a fluid can be atomized at a pressure of 5 to 60 MPa (50 to 600 bar), preferably 10 to 60 MPa (100 to 600 bar). The hydraulic diameter of the nozzle duct is less than 100 micrometers, preferably 1 to 20 micrometers. In the aerosol that is generated, the mean droplet diameter is less than 12 micrometers. The distribution of the droplet size can be adjusted in a reproducible manner. The aerosol can reach the lung, for example through inhaled air. However, the fluid droplets are difficult to precipitate from the air current onto a surface that meets with the aerosol-containing air current.
In WO 97/20590 a locking-stressing mechanism is described, which can be used for stressing a spring in a spring-actuated atomizer. The atomizer contains two housing parts, which are seated rotatable relative to one another. A helical spring is used for example as an energy storage means, which can be manually placed under tension with a screw-thrust transmission means by rotating the two housing parts toward each other. The locking-stressing mechanism is triggered manually by actuating a release button and displaces a piston in a cylinder, thus releasing a partial quantity of a fluid through a nozzle and atomizing it.